And there definitely is concern that one of these next two opponents will be able and willing to stick with the run and expose the Chargers’ rushing defense.

Sunday at Qualcomm Stadium, the NFL team allowing the most yards per carry faces Cincinnati’s sixth-ranked rushing offense. The Bengals, with Cedric Benson averaging 4.1 yards every time he runs, have rushed 430 times, third-most in the NFL. They are not likely to abandon the running game unless absolutely forced to.

Next week at Tennessee, Chris Johnson could be within a decent night of 2,000 yards. Johnson averages 6 yards per run, and the Titans have rushed fewer than 25 times in only three games this season.

“We’ve got to buckle up,” defensive lineman Travis Johnson said.

Through injury after injury up front and in the linebacker ranks, the Chargers have seen their overall numbers against the run improve since Pittsburgh ran for 177 yards in the season’s fourth game — most against San Diego since Nov. 4, 2007 (32 games).

Beginning with the next game, Oct. 19 against Denver, the Chargers have allowed an average of 102 rushing yards over the past nine games.

They brought in free agents Ian Scott and Alfonso Boone, got Johnson back from injury and established a defensive line rotation that has helped them more often than not dictate the line of scrimmage.

But this past Sunday at Dallas, the Chargers were thin on the line as Ogemdi Nwagbuo succumbed to an ankle injury and went on injured reserve and Boone sat out with a knee bruise.

And there have been issues with angles, discipline and missed tackles in the second level for a few weeks.

It can’t continue against these opponents.

“Guys have to take it upon themselves to do their job, get off blocks, stay in their gaps, tackle the guy with the ball,” linebacker Stephen Cooper said. “If we can’t do that, teams will continue establishing the run.”

The Chargers are allowing 5.1 yards per rush over the past four weeks, tied with the Arizona Cardinals for highest in the NFL in that span. For the season, the Chargers are all alone at the “top,” allowing a league-high 4.3 yards per carry.

In each of the past four games — against Denver, Kansas City, Cleveland and Dallas – there have been periods where those teams ran without much resistance.

On the drive in the second quarter when the Cowboys’ ultimately ran into a brick wall at the goal line, they nonetheless drove the 72 yards from their 27-yard line to the Chargers’ 1 on 12 rushes and a 4-yard penalty.

On its game-tying 99-yard drive to end the third quarter, Dallas got out of the shadow of the end zone with back-to-back runs of 10 and 9 yards.

In Dallas, the Chargers did not get the sizable lead they have most often enjoyed during their eight-game win streak. Thus, the Cowboys remained committed to the run until late in the fourth quarter, running a total of 27 times despite doing so just once in the final 15 minutes.

“It was a close game; we didn’t jump to a big lead,” defensive end Luis Castillo said. “We were playing against a big, physical offensive line and a couple of very good running backs. We didn’t expect to go out there and shut them down. We also do have to get things corrected and not give up as many big plays as we did, especially in big situations.”

While the Cowboys’ 4 yards per carry was actually the lowest average of the Chargers’ past four opponents, it was troubling the times Dallas’ backs gained 6 or more yards.

Scott was the Chargers’ only true nose tackle on Sunday, so rookie Vaughn Martin was put into a rotation there when he is best used as an end. With the Chargers having just five active linemen for the first time since that Oct. 4 game against Pittsburgh, every player had to work more snaps than is ideal.

Boone is expected back this week, and the Chargers hope to have newly acquired Antonio Garay ready to participate in at least a few series at tackle.

“I’m not just going to say us missing a couple guys, we should be able to go out there and let a team run on us because of it,” Castillo said. “ … The rotation has been great. But there’s no excuse. We still have players that can play.”